Method and application for improving surface morphology of Ga-containing alloy compound selective secondary epitaxy

Abstract

The present invention discloses a method for improving the surface morphology of selective secondary epitaxial growth of Ga-containing alloy compounds and its application. The method comprises: providing a heterojunction, the heterojunction comprises a channel layer and a barrier layer, the surface of the channel layer comprises a first region and a second region adjacent to the first region, the barrier layer is stacked in the first region of the channel layer, and a carrier channel is formed between the barrier layer and the channel layer; forming a first mask on the surface of the barrier layer, forming a second mask with lattice preferential orientation on the surface of the first mask, the second mask can make the precursor required for epitaxial growth of Ga-containing alloy compounds nucleate and grow; synchronously epitaxially growing Ga-containing alloy compounds on the second region of the channel layer and the second mask layer. The present invention avoids the problem of uneven thickness of Ga-containing alloy compounds grown in windows of different areas and the problem of large surface roughness caused by the migration of Ga atoms and N atoms during the growth process.

Description

Technical Field

[0001] The present invention particularly relates to a method for improving the surface morphology of secondary epitaxial growth of a Ga-containing alloy compound and its application, belonging to the field of micro-nano manufacturing technology. Background Art

[0002] In the manufacturing process of reducing the ohmic contact resistance of semiconductor devices, the best process method for reducing the source-drain ohmic contact resistance is currently the selective secondary epitaxial growth technology, such as Figure 1 As shown, using n + The total contact resistance of the GaN HEMT RF device obtained by -GaN secondary epitaxy technology is composed of the following three parts: metal and n + -GaN-GaN contact resistance (Rc), n + -GaN bulk resistance (Rn+GaN), n + -GaN to GaN heterojunction channel sidewall contact resistance (Rint).

[0003] The principle and process of epitaxial GaN using MOCVD (metal organic chemical vapor deposition) technology is as follows Figure 2 As shown, a gallium source (TMGa) and a nitrogen source (NH3) are usually introduced into a reaction chamber through a carrier gas. Under high temperature conditions, the gallium source decomposes into a precursor and a by-product of the reactant, and the precursor migrates on the substrate to generate GaN.

[0004] The existing routine + -GaN secondary epitaxy process flow Figure 3 As shown in FIG. 1 , a mask of insulating dielectric material (such as silicon oxide) is first deposited on the AlGaN / GaN heterojunction, the pattern is defined by photolithography, and then the mask and barrier layer are etched, and finally a secondary epitaxial growth of heavily doped GaN is performed in the source and drain electrode regions; however, in the selected area, the secondary epitaxial growth of n + -GaN, n- + -GaN thickness is different and the surface roughness is large, which seriously affects the device performance and test characterization. This is due to the obvious difference in the GaN growth mode inside the epitaxial window and on the mask, such as Figure 4 and Figure 5As shown in the figure, when using insulating dielectric materials such as silicon dioxide as a mask for selective secondary epitaxy, the MO source precursor (TMGa) shows extremely strong selective growth on the surface of the mask, does not nucleate on the mask surface, and grows on the GaN surface in the epitaxial window area, causing a more serious "window effect". Specifically, the reaction process of the MO source precursor on the mask surface can be divided into three categories: ① process: longitudinal diffusion of the precursor gas phase, ② process: lateral migration of the precursor on the mask surface, ③ process: adsorption and desorption of the precursor on the mask surface. These three processes work together, among which lateral migration has a greater impact on the window, resulting in a more obvious window effect. This results in a significant difference in the amount of Ga precursor on the mask surface and the epitaxial window surface, resulting in a rough n + -GaN / 2DEG channel interface has high contact resistance. The substrate in the epitaxial window is GaN. Generally speaking, homoepitaxial growth does not require nucleation and is directly stacked and grown in a two-dimensional manner. The growth of GaN on the mask outside the epitaxial window needs to go through the process of first forming a nucleation island, then the nucleation island continues to grow, and finally epitaxial growth into a thin film. There is an obvious difference in the time sequence of these two growth methods. The precursor is more inclined to grow in the epitaxial window, so the required binding energy is lower. Summary of the invention

[0005] The main purpose of the present invention is to provide a method for improving the surface morphology of Ga-containing binary / multinary alloy compounds by selective secondary epitaxial growth and its application, thereby overcoming the deficiencies in the prior art.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0007] In one aspect, the present invention provides a method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth, comprising:

[0008] Providing a heterojunction, the heterojunction comprising a channel layer and a barrier layer, the surface of the channel layer comprising a first region and a second region adjacent to the first region, the barrier layer being stacked on the first region of the channel layer, and a carrier channel being formed between the barrier layer and the channel layer;

[0009] forming a first mask on the surface of the barrier layer, and forming a second mask with a lattice preferred orientation on the surface of the first mask, wherein the second mask can enable the nucleation growth of a precursor required for epitaxial growth of a Ga-containing binary / multinary alloy compound;

[0010] Synchronously, an n-type doped Ga-containing binary / multinary alloy compound is epitaxially grown on the second region of the channel layer and the second mask layer to form an n-type doped Ga-containing binary / multinary alloy compound layer, wherein the Ga-containing binary / multinary alloy compound further comprises at least one element of N, Al, and In.

[0011] Another aspect of the present invention provides a method for reducing the ohmic contact resistance of a semiconductor device, comprising:

[0012] The epitaxial structure of a semiconductor device is obtained by using the method for improving the surface morphology of the selected secondary epitaxial growth of a Ga-containing binary / multinary alloy compound, wherein the epitaxial structure includes a heterojunction and an n-type doped Ga-containing binary / multinary alloy compound layer formed by secondary epitaxy, and the n-type doped Ga-containing binary / multinary alloy compound layer serves as an ohmic electrode of the semiconductor device;

[0013] A metal electrode is formed on the n-type doped Ga-containing binary / multinary alloy compound layer, and the metal electrode is in ohmic contact with the n-type doped Ga-containing binary / multinary alloy compound layer.

[0014] Compared with the prior art, the advantages of the present invention include:

[0015] 1) The method provided by the present invention for improving the surface morphology of selective secondary epitaxial growth of Ga-containing binary / multinary alloy compounds can better protect the AlGaN / GaN channel without affecting the mobility and channel resistance of the channel.

[0016] 2) The method provided by the present invention for improving the surface morphology of selective secondary epitaxial growth of Ga-containing binary / multinary alloy compounds has low cost and high efficiency and is suitable for large-scale production.

[0017] 3) The method provided by the present invention for improving the surface morphology of selective secondary epitaxial growth of Ga-containing binary / multinary alloy compounds has a simple process and a larger process window. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of GaN HEMT RF device and its total contact resistance;

[0019] Figure 2 It is a schematic diagram of the principle and process of epitaxial growth of GaN using MOCVD technology;

[0020] Figure 3 This is a schematic diagram of the conventional process flow for performing secondary epitaxy of n+-GaN;

[0021] Figure 4 It is a schematic diagram of the diffusion process of MO source precursor on the surface of silicon dioxide mask;

[0022] Figure 5 The schematic diagram is that the migration of MO source precursor on the mask surface causes the film in the epitaxial window to present a saddle shape;

[0023] Figure 6It is a schematic diagram of a preparation process of a GaN HEMT radio frequency device provided in a typical implementation case of the present invention;

[0024] Figure 7 are HRXRD test results of the AlN masks formed by deposition in Examples 1 to 3 of the present invention;

[0025] Figure 8 This is the SEM test result of the sample obtained by epitaxial growth of GaN using an AlN mask with a thickness of 10nm;

[0026] Figure 9a This is the SEM test result of the sample obtained by epitaxial growth of GaN using an AlN mask with a thickness of 35nm;

[0027] Figure 9b This is the AFM test result of the sample obtained by epitaxial growth of GaN using an AlN mask with a thickness of 35nm;

[0028] Fig.10a This is the SEM test result of the sample obtained by epitaxial growth of GaN using an AlN mask with a thickness of 75nm;

[0029] Fig.10b This is the AFM test result of the sample obtained by epitaxial growth of GaN using an A1N mask with a thickness of 75nm;

[0030] Fig.11a This is the SEM test result of the sample obtained by epitaxial growth of GaN using silicon oxide with a thickness of 200 nm as a mask in Comparative Example 1;

[0031] Fig.11b This is the AFM test result of the sample obtained by epitaxial growth of GaN using silicon oxide with a thickness of 200 nm as a mask in Comparative Example 1. DETAILED DESCRIPTION

[0032] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0033] In one aspect, the present invention provides a method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth, comprising:

[0034] Providing a heterojunction, the heterojunction comprising a channel layer and a barrier layer, the surface of the channel layer comprising a first region and a second region adjacent to the first region, the barrier layer being stacked on the first region of the channel layer, and a carrier channel being formed between the barrier layer and the channel layer;

[0035] forming a first mask on the surface of the barrier layer, and forming a second mask with a lattice preferred orientation on the surface of the first mask, wherein the second mask can enable the nucleation growth of a precursor required for epitaxial growth of a Ga-containing binary / multinary alloy compound;

[0036] Synchronously, an n-type doped Ga-containing binary / multinary alloy compound is epitaxially grown on the second region of the channel layer and the second mask layer to form an n-type doped Ga-containing binary / multinary alloy compound layer, wherein the Ga-containing binary / multinary alloy compound further comprises at least one element of N, Al, and In.

[0037] Furthermore, the material of the first mask is a dielectric insulating material.

[0038] Furthermore, the material of the first mask includes silicon oxide or silicon nitride.

[0039] Furthermore, the method for improving the surface morphology of the selective secondary epitaxial growth of Ga-containing binary / multinary alloy compounds specifically includes: depositing the second mask on the first mask by physical vapor deposition, metal organic compound chemical vapor deposition, or molecular beam epitaxy.

[0040] Furthermore, the method for improving the surface morphology of the selective secondary epitaxial growth of Ga-containing binary / multinary alloy compounds specifically includes: depositing the second mask on the first mask by magnetron sputtering.

[0041] Furthermore, the material of the second mask includes a binary / multinary alloy compound containing two or more elements of Al, N, Ga, and In.

[0042] Furthermore, the material of the second mask includes AlN, InAlN, ScAlN, GaN or InGaN, and AlN is particularly preferred as the second mask. This is because the deposition temperature of AlN deposited by magnetron sputtering is relatively low, generally around 250°C, and the epitaxial temperature of MOCVD grown AlN film is relatively high, which will accelerate the diffusion of A1 on one side of the AlGaN barrier layer to the GaN channel layer side, causing damage to the AlGaN / GaN channel, blurring the boundary of the channel, resulting in reduced channel mobility and increased channel resistance. In addition, the cost of growing AlN film by MOCVD is high, which is not conducive to reducing costs. The method of controlling the area effect and roughness by changing the carrier gas is difficult, and the process window is difficult to explore.

[0043] Furthermore, the thickness of the second mask is greater than 10 nm.

[0044] Furthermore, the method for improving the surface morphology of the selected secondary epitaxial growth of Ga-containing binary / multinary alloy compounds specifically includes: using metal organic compound chemical vapor deposition and molecular beam epitaxy to simultaneously epitaxially grow n-type doped Ga-containing binary / multinary alloy compounds on the second region of the channel layer and the second mask layer.

[0045] Furthermore, a top surface of the n-type doped Ga-containing binary / multinary alloy compound layer located in the second region of the channel layer is located on a side of the interface between the barrier layer and the first mask close to the barrier layer.

[0046] Furthermore, the n-type doped Ga-containing binary / multinary alloy compound includes n + -GaN, n + -InGaN, n + -AlGaN or n + -InAlGaN.

[0047] Further, the channel layer includes a first portion and a second portion adjacent to the first portion, the first portion corresponds to the first region, the second portion corresponds to the second region, and the thickness of the first portion is greater than the thickness of the second portion.

[0048] In a more typical embodiment, the method for improving the surface morphology of the selective secondary epitaxial growth of Ga-containing binary / multinary alloy compounds specifically includes: forming a stacked barrier layer, a first mask, and a second mask in sequence on the channel layer, and removing the second mask, the first mask, the barrier layer, and a portion of the channel layer located in the first area to expose the first portion of the channel layer.

[0049] Furthermore, a top surface of the first portion of the channel layer is located on a side of the carrier channel facing away from the barrier layer.

[0050] Furthermore, the method for improving the surface morphology of the selective secondary epitaxial growth of Ga-containing binary / multinary alloy compounds further comprises: after the growth of the n-type doped Ga-containing binary / multinary alloy compound, removing the first mask and the second mask.

[0051] Another aspect of the present invention provides a method for reducing the ohmic contact resistance of a semiconductor device, comprising:

[0052] The epitaxial structure of a semiconductor device is obtained by using the method for improving the surface morphology of the selected secondary epitaxial growth of a Ga-containing binary / multinary alloy compound, wherein the epitaxial structure includes a heterojunction and an n-type doped Ga-containing binary / multinary alloy compound layer formed by secondary epitaxy, and the n-type doped Ga-containing binary / multinary alloy compound layer serves as an ohmic electrode of the semiconductor device;

[0053] A metal electrode is formed on the n-type doped Ga-containing binary / multinary alloy compound layer, and the metal electrode is in ohmic contact with the n-type doped Ga-containing binary / multinary alloy compound layer.

[0054] Furthermore, the first region is a source and drain electrode region of the epitaxial structure.

[0055] Furthermore, the semiconductor device includes a HEMT radio frequency device, a power device or a Schottky diode.

[0056] The technical solution, its implementation process and principles, etc. will be further explained below in conjunction with the accompanying drawings and specific implementation cases. Unless otherwise specified, the MOCVD (metal organic chemical vapor deposition) equipment, PVD (physical vapor deposition) equipment, etc. used in the embodiments of the present invention are all known to those skilled in the art, and their equipment structures are not described in detail here.

[0057] Example 1

[0058] See also Figure 6 , a method for preparing a GaN HEMT radio frequency device, comprising the following steps:

[0059] 1) Provide AlGaN / GaN heterojunction HEMT wafers.

[0060] Specifically, the stacked GaN channel layer and the AlGaN barrier layer may be grown in sequence by MOCVD, and the specific growth process and growth parameters are not limited here.

[0061] 2) Silicon oxide with a thickness of 200 nm is deposited on the surface of the GaN channel layer as a first mask (the first mask is a hard mask).

[0062] 3) A 10 nm thick AlN is deposited on the surface of the first mask by magnetron sputtering as the second mask. The specific magnetron sputtering equipment and process parameters are not limited here.

[0063] 4) The second mask corresponding to the source electrode region and the drain electrode region is removed by photolithography and etching to expose the first mask corresponding to the source electrode region and the drain electrode region. The region where the first mask is removed is the secondary epitaxial region.

[0064] 5) The first mask exposed in the source electrode region and the drain electrode region is removed by etching to expose the AlGaN barrier layer.

[0065] 6) Etching and removing the AlGaN barrier layer and part of the GaN channel layer exposed in the source electrode region and the drain electrode region, and etching until below the carrier channel in the GaN channel layer.

[0066] 7) The epitaxial structure obtained in step 6) is transferred to the growth chamber of the MOCVD device, and epitaxial growth is performed simultaneously on the surface of the GaN channel layer exposed in the source electrode region and the drain electrode region and the surface of the remaining second mask. + -GaN, then remove the first mask, the second mask, and the n-GaN grown on the second mask. + -GaN.

[0067] 8) n in the source electrode region and the drain electrode region respectively + Ti / Al / Ni / Au is deposited on n+GaN as a metal electrode, and the metal electrode forms an ohmic contact with n+GaN.

[0068] Example 2

[0069] See also Figure 6 , a method for preparing a GaN HEMT radio frequency device, comprising the following steps:

[0070] 1) Provide AlGaN / GaN heterojunction HEMT wafers.

[0071] Specifically, the stacked GaN channel layer and the AlGaN barrier layer may be grown in sequence by MOCVD, and the specific growth process and growth parameters are not limited here.

[0072] 2) Silicon oxide with a thickness of 200 nm is deposited on the surface of the GaN channel layer as a first mask (the first mask is a hard mask).

[0073] 3) A 35 nm thick AlN is deposited on the surface of the first mask by magnetron sputtering as the second mask. The specific equipment and process parameters of the magnetron sputtering are not limited here.

[0074] 4) The second mask corresponding to the source electrode region and the drain electrode region is removed by photolithography and etching to expose the first mask corresponding to the source electrode region and the drain electrode region. The region where the first mask is removed is the secondary epitaxial region.

[0075] 5) The first mask exposed in the source electrode region and the drain electrode region is removed by etching to expose the AlGaN barrier layer.

[0076] 6) Etching and removing the AlGaN barrier layer and part of the GaN channel layer exposed in the source electrode region and the drain electrode region, and etching until below the carrier channel in the GaN channel layer.

[0077] 7) The epitaxial structure obtained in step 6) is transferred to the growth chamber of the MOCVD device, and epitaxial growth is performed simultaneously on the surface of the GaN channel layer exposed in the source electrode region and the drain electrode region and the surface of the remaining second mask. + -GaN, then remove the first mask, the second mask, and the n-GaN grown on the second mask. + -GaN.

[0078] 8) n in the source electrode region and the drain electrode region respectively + -GaN is deposited with Ti / Al / Ni / Au as metal electrodes, and the metal electrodes are connected to n + -GaN forms an ohmic contact.

[0079] Example 3

[0080] See also Figure 6 , a method for preparing a GaN HEMT radio frequency device, comprising the following steps:

[0081] 1) Provide AlGaN / GaN heterojunction HEMT wafers.

[0082] Specifically, the stacked GaN channel layer and the AlGaN barrier layer may be grown in sequence by MOCVD, and the specific growth process and growth parameters are not limited here.

[0083] 2) Silicon oxide with a thickness of 200 nm is deposited on the surface of the GaN channel layer as a first mask (the first mask is a hard mask).

[0084] 3) A 75 nm thick AlN is deposited on the surface of the first mask by magnetron sputtering as the second mask. The specific magnetron sputtering equipment and process parameters are not limited here.

[0085] 4) The second mask corresponding to the source electrode region and the drain electrode region is removed by photolithography and etching to expose the first mask corresponding to the source electrode region and the drain electrode region. The region where the first mask is removed is the secondary epitaxial region.

[0086] 5) The first mask exposed in the source electrode region and the drain electrode region is removed by etching to expose the AlGaN barrier layer.

[0087] 6) Etching and removing the AlGaN barrier layer and part of the GaN channel layer exposed in the source electrode region and the drain electrode region, and etching until below the carrier channel in the GaN channel layer.

[0088] 7) The epitaxial structure obtained in step 6) is transferred to the growth chamber of the MOCVD device, and epitaxial growth is performed simultaneously on the surface of the GaN channel layer exposed in the source electrode region and the drain electrode region and the surface of the remaining second mask. + -GaN, then remove the first mask, the second mask, and the n-GaN grown on the second mask. + -GaN.

[0089] 8) n in the source electrode region and the drain electrode region respectively + Ti / Al / Ni / Au is deposited on n+GaN as a metal electrode, and the metal electrode forms an ohmic contact with n+GaN.

[0090] HRXRD tests were performed on the AlN masks formed by deposition in Examples 1 to 3, respectively. The test results are shown in FIG. Figure 7 As shown by Figure 7 It can be seen that a diffraction peak can be observed at 36.02°, which indicates that the AlN film formed by sputtering at this time has a certain preferred orientation (002) plane, which is similar to the AlN film epitaxially grown using MOCVD. Therefore, it can be judged that GaN can achieve nucleation epitaxial growth on the sputtered AlN film.

[0091] The inventors of this case also used other AlN masks with different thicknesses to perform GaN selective epitaxy. The inventors of this case found that the SEM test results of the samples obtained by using the AlN mask with a thickness of 10nm for GaN epitaxial growth are as follows: Figure 8 As shown in the figure, it can be seen that there is no obvious GaN deposition on the surface of AlN. At this time, the GaN epitaxy rate in the window is very fast and the surface is relatively rough. The SEM test results of the samples obtained by using AlN masks with thicknesses of 35nm and 75nm for GaN epitaxial growth are shown in Figure 1. Figure 9a , Fig.10a As shown, it can be found that the overall surface of the sample is relatively smooth. It can be seen that the use of an AlN mask with a thickness of 10 nm did not achieve the desired effect. It is speculated that the reason may be that the epitaxial temperature is too high, the AlN mask is too thin, and the quality of the AlN film prepared by sputtering is poor, resulting in thermal decomposition of AlN during the epitaxial process, resulting in the failure to achieve GaN nucleation growth in the AlN mask.

[0092] The AFM test results of the samples obtained by epitaxial growth of GaN using an A1N mask with a thickness of 35 nm and the samples obtained by epitaxial growth of GaN using an A1N mask with a thickness of 75 nm are as follows: Figure 9b , Fig.10bAs shown in the figure, it can be found that the surface roughness of the sample grown using an AlN mask with a thickness of 35nm is 1.34nm, while the surface roughness of the sample grown using an AlN mask with a thickness of 75nm is 0.869nm. The surface of the GaN film epitaxially grown using two AlN masks of different thicknesses has holes, but the surface roughness of the sample epitaxially grown using an AlN mask with a thickness of 75nm is lower and the surface is smoother. The improvement in morphology is largely due to the fact that the precursor can nucleate and grow on AlN, which shortens the diffusion length of the Ga source.

[0093] It should be noted that the inventors of this case also referred to Examples 1 to 3 and used n+-InGaN or n+-AlGaN as the n-type doped Ga-containing binary / multinary alloy compound and InAlN, ScAlN, GaN, or InGaN as the second mask to prepare GaN HEMT RF devices. The results after selective area epitaxy were basically consistent with those of Examples 1 to 3.

[0094] Comparative Example 1

[0095] See also Figure 3 , a method for preparing a GaN HEMT radio frequency device, comprising the following steps:

[0096] 1) Provide AlGaN / GaN heterojunction HEMT wafers.

[0097] Specifically, the stacked GaN channel layer and the AlGaN barrier layer may be grown in sequence by MOCVD, and the specific growth process and growth parameters are not limited here.

[0098] 2) Deposit 200 nm thick silicon oxide on the surface of the GaN channel layer as a mask.

[0099] 3) The mask exposed in the source electrode region and the drain electrode region is removed by etching to expose the AlGaN barrier layer.

[0100] 4) Etching and removing the AlGaN barrier layer and part of the GaN channel layer exposed in the source electrode region and the drain electrode region, and etching until below the carrier channel in the GaN channel layer.

[0101] 5) The epitaxial structure obtained in step 4) is transferred to the growth chamber of the MOCVD device, and epitaxial growth is performed simultaneously on the surface of the GaN channel layer exposed in the source electrode region and the drain electrode region and on the surface of the remaining mask. + -GaN, and then remove the mask and other structural layers on the mask.

[0102] 6) n in the source electrode region and the drain electrode region respectively +Ti / Al / Ni / Au is deposited on n+GaN as a metal electrode, and the metal electrode forms an ohmic contact with n+GaN.

[0103] When using silicon dioxide as a mask for selective secondary epitaxy, the MO source precursor (TMGa) grows extremely selectively on the surface of the mask, does not nucleate on the silicon dioxide surface, and grows on the GaN surface in the window area, resulting in a more serious "window effect".

[0104] Comparative Example 1: GaN epitaxial growth was performed using silicon oxide with a thickness of 200 nm as a mask. The SEM test results of the sample surface after GaN epitaxial growth are as follows: Fig.11a As shown in Figure 2, the AFM test results are as follows: Fig.11b As shown by Fig.11a It can be seen that the surface of the sample is very rough and has many holes. Fig.11b It can be learned that the roughness of the sample surface is 98.1 nm.

[0105] The present invention provides a method for improving the surface morphology of selective secondary epitaxial growth of Ga-containing binary / multinary alloy compounds. The method uses a PVD method to sputter a binary / multinary alloy compound mask such as AlN on a SiO2 hard mask, thereby avoiding damage to a channel caused by high temperature, and has low cost and simple process. The Ga-containing binary / multinary alloy compounds such as n+GaN are not only nucleated in an etching window area, but also grow synchronously on the surface of the binary / multinary alloy compound mask such as AlN, which is close to whole-piece epitaxy, thereby avoiding the problem of uneven thickness of Ga binary / multinary alloy compounds such as n+GaN grown in windows of different areas due to the migration of Ga atoms and N atoms during the growth process and the problem of large surface roughness.

[0106] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth, characterized in that: include: Providing a heterojunction, the heterojunction comprising a channel layer and a barrier layer, the surface of the channel layer comprising a first region and a second region adjacent to the first region, the barrier layer being stacked on the first region of the channel layer, and a carrier channel being formed between the barrier layer and the channel layer; A first mask is formed on the surface of the barrier layer, and a second mask having a lattice preferred orientation is deposited on the surface of the first mask by physical vapor deposition, metal organic compound chemical vapor deposition, or molecular beam epitaxy, wherein the material of the second mask includes a binary / multinary alloy compound containing two or more elements of Al, N, Ga, and In, the thickness of the second mask is greater than 10 nm, and the second mask can enable the precursor required for epitaxial growth of the Ga-containing binary / multinary alloy compound to nucleate and grow; Synchronously, an n-type doped Ga-containing binary / multinary alloy compound is epitaxially grown on the second region of the channel layer and the second mask layer to form an n-type doped Ga-containing binary / multinary alloy compound layer, wherein the Ga-containing binary / multinary alloy compound further comprises at least one element of N, Al, and In.

2. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 1, characterized in that: The material of the first mask is a dielectric insulating material.

3. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 2, characterized in that: The material of the first mask includes silicon oxide or silicon nitride.

4. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 1, characterized in that: include: The second mask is formed by depositing on the first mask by magnetron sputtering.

5. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 1 or 4, characterized in that: The material of the second mask includes AlN, InAlN, ScAlN, GaN or InGaN.

6. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 1, characterized in that: include: An n-type doped Ga-containing binary / multinary alloy compound is epitaxially grown synchronously on the second region of the channel layer and the second mask layer by means of metal organic compound chemical vapor deposition and molecular beam epitaxy.

7. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 6, characterized in that: A top surface of the n-type doped Ga-containing binary / multinary alloy compound layer located in the second region of the channel layer is located on a side of an interface between the barrier layer and the first mask close to the barrier layer.

8. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 6, characterized in that: The n-type doped Ga-containing binary / multinary alloy compound comprises n + -GaN, n + -InGaN, n + -AlGaN or n + -InAlGaN.

9. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 1, characterized in that: The channel layer includes a first portion and a second portion adjacent to the first portion, the first portion corresponds to the first region, the second portion corresponds to the second region, and a thickness of the first portion is greater than a thickness of the second portion.

10. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 9, characterized in that: The method comprises: sequentially forming a barrier layer, a first mask and a second mask stacked on the channel layer, and removing the second mask, the first mask, the barrier layer and a portion of the channel layer located in the first area to expose the first portion of the channel layer.

11. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 9, characterized in that: A top surface of the first portion of the channel layer is located on a side of the carrier channel facing away from the barrier layer.

12. The method for improving the surface morphology of Ga-containing binary / multinary alloy compound selective secondary epitaxial growth according to claim 1, characterized in that: Also includes: After the n-type doped Ga-containing binary / multinary alloy compound is grown, the first mask and the second mask are removed.

13. A method for reducing the ohmic contact resistance of a semiconductor device, characterized in that: include: The epitaxial structure of a semiconductor device is obtained by using the method for improving the surface morphology of the selective secondary epitaxial growth of a Ga-containing binary / multinary alloy compound as described in any one of claims 1 to 12, wherein the epitaxial structure comprises a heterojunction and an n-type doped Ga-containing binary / multinary alloy compound layer formed by secondary epitaxy, and the n-type doped Ga-containing binary / multinary alloy compound layer serves as an ohmic electrode of the semiconductor device; A metal electrode is formed on the n-type doped Ga-containing binary / multinary alloy compound layer, and the metal electrode is in ohmic contact with the n-type doped Ga-containing binary / multinary alloy compound layer.

14. The method for reducing the ohmic contact resistance of a semiconductor device according to claim 13, characterized in that: The first region is the source and drain electrode region of the epitaxial structure.

15. The method for reducing the ohmic contact resistance of a semiconductor device according to claim 13, characterized in that: The semiconductor device includes a HEMT radio frequency device, a power device or a Schottky diode.

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